Abstract
Over the two past decades, a significant number of studies have observed animal growth traits to examine animal genetic mechanisms due to their ease of measurement and high heritability. Chicken which has a significant impact on fundamental biology is a major source of protein worldwide, making it an ideal model for examining animal growth trait development. The genetic mechanisms of chicken growth traits have been studied using quantitative trait loci mapping through genome-scan and candidate gene approaches, genome-wide association studies (GWAS), comparative genomic strategies, microRNA (miRNA) regulation of growth development analysis, and epigenomic analysis. This review focuses on chicken GWAS and miRNA regulation of growth traits. Several recently published GWAS reports showed that most genome-wide significant single nucleotide polymorphisms are located on chromosomes 1 and 4 in chickens. Chicken growth, particularly skeletal muscle growth and development, is greatly regulated by miRNA. Using dwarf and normal chickens, let-7b was found to be involved in determining chicken dwarf phenotypes by regulating growth hormone receptor gene expression.
Highlights
The growth and development of livestock is a complicated life process and is subject to a significant amount of genetic control
A number of single nucleotide polymorphisms (SNPs) located within genes encoding for growth hormone (GH) and its receptor (GHR), ghrelin (GHRL) and its receptor (GHSR), insulin-like growth factor 1 (IGF-1) and its receptor (IGF1R), insulin (INS), insulin-like growth factor binding protein
No indication of an association between either SNP A17299834G or SNP C17293932T and the IGF-IR gene was observed for growth traits; haplotypes could be constructed from these two SNPs, which were shown to be significantly associated with body weights, daily weight gains, and leg length [9]
Summary
The growth and development of livestock is a complicated life process and is subject to a significant amount of genetic control. One 57-bp indel in intron 2 of the PIT1 gene was reported to be significantly associated with hatch weight and shank length at 84 d of age [8] Another 6-bp indel of the GHSR gene was found to be related to crude fatty content of the leg muscle, no evidence for its association with growth traits was identified [7]. No indication of an association between either SNP A17299834G or SNP C17293932T and the IGF-IR gene was observed for growth traits; haplotypes could be constructed from these two SNPs, which were shown to be significantly associated with body weights, daily weight gains, and leg length [9]. Using high-resolution QTL is effective for identifying quantitative traits near genes
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